Bill Read's Blog: Isaac's Strength

Today will be a very busy day along the Gulf Coast as communities prepare for the eventual landfall of Isaac. The center of Isaac is expected to make landfall late Tuesday night or Wednesday morning, however, because Isaac is a large storm adverse conditions will begin overspreading the northern gulf coast as early as Tuesday morning. While the current forecast has the center of Isaac making landfall in southeast Louisiana, there is an unusual amount of uncertainty in eventual track for a large storm with only a short time to go before landfall, keeping most of Louisiana, Mississippi, and Alabama coastal communities at risk. By later today, it will be clearer where the precise track at landfall will be.

How strong will Isaac be? Our best computer models continue to forecast steady strengthening with Isaac reaching around 90 to 100 mph before reaching the coast. Indeed, warmer Gulf waters and an expected favorable wind environment along the path across the eastern Gulf of Mexico support this forecast. However, working against this trend has been a lack of organization of the strong thunderstorms near the center. While satellite imagery shows some strengthening may be underway, as of early this morning, Isaac still hadn’t developed an eye wall. I have noticed in the past that storms of a large size without a well-defined inner core frequently struggle to gain an inner core and higher winds. Let’s hope that is the case with Isaac. Hurricane Hunter aircraft will be continuously flying Isaac and will give us the valuable information needed to determine if and when the anticipated intensification is underway.

Near and well to the east of where Isaac’s center makes landfall significant storm surge flooding of 4 to 6 feet will be widespread. Some highly vulnerable areas where the strongest winds occur surge could reach up to 12 feet. While not in Katrina’s class, those living near the coast will suffer the effects of this surge. Because of Isaac’s size, it is forecast to slow down considerably at and after landfall, extremely heavy rainfall of 10 to 15 inches and perhaps more than 20 inches could fall in some locations over the next several days causing widespread fresh water flooding. Power outages, trees down and structural damage to poorly constructed building can be expected from Isaac’s winds.

If Isaac tracks further west than the current forecast, we could experience the fringe effects of the west side the storm on Wednesday. The early morning forecast had our area in a 10-20 percent chance of experiencing tropical storm conditions on Wednesday. Stay tuned!